It has been recognized in the prior art that kinetic energy of a vehicle can be stored as potential energy during braking of the vehicle and then later used to power the vehicle. By utilizing energy that would normally be dissipated as heat in the vehicle brakes, the use of this stored energy reduces the amount of primary energy required to propel the vehicle. For an example of the type of regenerative braking system, reference is made to U.S. Pat. No. 4,246,988 to Hoppie.
It has also been recognized that kinetic energy can be derived from the vehicle during normal vehicle operation, such as during coasting, such energy being likewise stored for subsequent use in reducing power requirements from the engine. An example of this type of system is found in U.S. Pat. No. 3,734,222 to Bardwick. Other patents concerned with this subject matter are U.S. Pat. Nos. 4,098,144 (to Besel et al.) and 4,159,042 (to Jayner).
The systems in the aforementioned Bardwick and Besel et al patents employ one or more inertial flywheels for energy storage and selectively interconnect the vehicle drive shaft to the flywheels in driven or driving relation by means controlled gearing and braking arrangements. The flywheel storage approach has not been received with great success because it requires a relatively complex energy transfer mechanism which is subject to failure and which is relatively inefficient so as to dissipate a considerable proportion of the transferred energy. This has led experimenters to use elastomeric storage devices for storing the energy. The aforementioned Hoppie and Jayner patents disclose such storage devices in the form of solid elastomeric bodies which are either torsionally stressed, as in Hoppie, or longitudinally stressed, as in Jayner. While these elastomeric storage devices appear fine in concept, their deployment brings about many practical problems. Specifically, longitudinal stressing requires bulky, complicated and awkwardly shaped storage devices to permit storage of any meaningful amount of energy. A solid elastomeric device, stressed torsionally, experiences zero stress at the axis and only at the surface can the material be fully stressed. Consequently, energy storage per pound of elastomer is low. Further, a solid elastomeric element must be kept relatively short and wound only a few turns to be kept stable. Thus, an extremely high gear ratio, from engine shaft speed to turns of the storage device, is mandatory.
Apart from the practical problems noted above, the systems described in all of the aforementioned patents require separate energy transmission paths for energy delivery to and transfer from the storage device. The dual paths involve space consumption, high cost, and energy losses.
In U.S. Pat. No. 3,126,070 there is disclosed an energy storage device wherein a rubber tube is bonded at each end to respective cap for a shaft about which the tube is rotatably slidable. The caps are rotatable relative to the shaft but can be individually locked so that the rubber tube can be torsionally stressed or torsionally relaxed. To my knowledge, no one has considered a hollow elastomeric tube for use for vehicle energy recovery. Certainly Hayek did not consider use of the tube with such large loads since Hayek discusses the use of his device for mechanical toys, clocks, and the like. The relatively simple connection of the tube to the end caps, and simple ratchet arrangements to preclude unintended energy release, would, in any case, preclude the use of the Hayek device for any heavy load operation such as vehicle energy recovery. Moreover, since Hayek requires delivery and removal of energy to be achieved at opposite ends of the device, the problem of separate energy flow paths, with the disadvantages noted above, remains.